I am a mod translator, when I change the language from English to Chinese, I was surprised to found that all entries in the book have not changed, reload the resource pack also is useless.
By reading the source code, it seems that the book's entry is load when registered the item.
I hope to add a hot reload function (maybe a command is better).

Strange. Nothing should be cached. It's all translated on the fly.

Nevermind I'm actually just stupid.